Shop-owners in cities across the US are boarding up windows as they brace for unrest following the US election.

The preparations come just a few months after many businesses were hit by looters in the violent demonstrations that erupted after the death of George Floyd at the hands of police.

Retailers Saks 5th Avenue, Nordstrom and pharmacy chain CVS were among the biggest firms taking precautions.

Concerns the election will be contested have also weighed on financial markets.

However, the main US indexes closed higher on Monday, reversing course after steep falls last week.

National polls suggest a healthy lead for challenger Joe Biden over current US President Donald Trump in Tuesday's election.

But Mr Biden's lead is narrower in the handful of states that could decide the result. Legal disputes over what votes will be counted are already under way in many states.

In 2000, when a recount fight in Florida raised uncertainty about the outcome of the US election, financial markets sank by about 5%, said Brian Gardner, chief Washington policy strategist at investment bank Stifel.

Mr Gardner is predicting a Biden victory but warned that questions about the result and any outbreak of violence could cause a steeper fall this time around.

Walmart last week said it was temporarily removing guns and ammunition from display in thousands of its stores in the United States, citing concerns of "civil unrest". A day later, however, it reversed the decision.

In recent days, Australia's Department of Foreign Affairs updated its travel advisories, warning citizens against travel to the US in part due to anticipated violence.

"Take precautions to keep safe during the election season," it says. "Avoid areas where protests and demonstrations are occurring."

More than 96 million Americans have already cast their ballots in early voting, putting the country on course for its highest turnout in a century.